[bzoj3790]神奇项链

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 #define N 100005
 4 #define mod 1000000007
 5 pair<int,int>hw[N];
 6 int n,ma,ans,s1[N],s2[N],mi[N];
 7 char s[N],ss[N]; 
 8 int hash1(int x,int y){
 9     return (s1[y]-1LL*s1[x]*mi[y-x]%mod+mod)%mod;
10 }
11 int hash2(int x,int y){
12     return (s2[y]-1LL*s2[x]*mi[x-y]%mod+mod)%mod;
13 }
14 int main(){
15     while (scanf("%s",ss)!=EOF){
16         n=0;
17         for(int i=0;ss[i];i++){
18             s[++n]=‘{‘;
19             s[++n]=ss[i];
20         }
21         s[++n]=‘{‘;
22         s2[n+1]=0;
23         mi[0]=1;
24         for(int i=1;i<=n;i++)mi[i]=mi[i-1]*29LL%mod;
25         for(int i=1;i<=n;i++)s1[i]=(s1[i-1]*29LL+s[i]-‘a‘)%mod;
26         for(int i=n;i;i--)s2[i]=(s2[i+1]*29LL+s[i]-‘a‘)%mod;
27         for(int i=1;i<=n;i++){
28             int l=0,r=min(i,n-i);
29             while (l<r){
30                 int mid=(l+r+1>>1);
31                 if (hash1(i,i+mid)==hash2(i,i-mid))l=mid;
32                 else r=mid-1;
33             }
34             hw[i]=make_pair(i-l,i+l);
35         }
36         sort(hw+1,hw+n+1);
37         ma=ans=0;
38         for(int i=1,j=1;i<=n;i++){
39             if (hw[i].first>j){
40                 j=ma;
41                 ma=0;
42                 ans++;
43             }
44             if (hw[i].second>j)ma=max(ma,hw[i].second);
45         }
46         printf("%d\n",ans-1);
47     }
48 }